Some people shake with anticipation; Sir Cameron Mackintosh sways. The theatre is quiet, momentarily, but the tunes in his head never stop. This afternoon's toe-tapper, which we're about to hear, is a particularly jaunty number, as I am to learn to my cost when trying to get to sleep later that night. We're standing in the dress circle of London's Novello, waiting for his director, the indomitable Sir Richard Eyre, to finish a group hug with the cast of Betty Blue Eyes before they break into the song that's already ringing in his ears.
If the musical lacks the jingle-jogging power of the likes of Les Misérables or Phantom, then it's probably only a matter of time. The work is the latest to join Sir Cameron's stable, and it would take a brave man to bet against it becoming another hit. Just consider its pedigree: the show is based on Alan Bennett's 1984 film A Private Function, and is the brainchild of a talented quartet of writers, which intriguingly include two Americans; intriguingly, because it's hard to imagine a more home-grown affair than this homage to post-war Britain.
For starters, the story's backdrop is a royal wedding: Prince Philip's to Princess Elizabeth. Sir Cameron, who issued the Betty Blue Eyes press release barely hours before news broke of Prince William's own impending nuptials, is aware he could hardly have timed it better. He stops swaying, briefly, to lean over and whisper: "I've heard from inside," cue theatrical pause from this most theatrical of men, "that even the Queen didn't know."
Then there's the Austerity Britain milieu. It's 1947 and rationing is in full swing. But the venal councillors don't let that stop them from secretly fattening a pig for slaughter in expectation of the big day's celebrations.
And then, suddenly, the cast disperses and we're left staring at a giant reproduction of the Second World War maxim that the population should "Keep Calm and Carry On" before the two leads, Sarah Lancashire and Reece Shearsmith, start belting out "Another Little Victory for Little England". Or perhaps I should say three leads: a few bars in and a squealing pig, the blue-eyed Betty of the title, joins in, helping me to surmise that the victory in question is the couple's heist of said pig.
Before animal lovers get carried away, the Betty on the stage is the work not of nature but an Australian-based animatronics company, Creature Technology. Not that that lessens her appeal: "She's a very precious girl!" Sir Cameron insists, during our chat earlier in one of the theatre's antechambers, a bizarrely faux country house-decorated room, complete with chintzy armchairs. "You completely believe she's real, and you actually get upset when she's squealing because someone is trying to cut her throat. We treat her as a real person. In fact, one of the characters leaves his wife for her."
Despite Betty's starring role in the publicity posters, the show is about more than just her. "The pig is the pivot for it, in the way that Cosette is the pivot for Les Misérables, but Les Misérables isn't the story of Cosette, is it?" Sir Cameron says. As for the story, the producer thinks the American duo behind it, Ron Cowen and Daniel Lipman, who wrote the script for the US version of the TV comedy Queer As Folk, struck gold almost accidentally. "Being Americans, they had no idea how much of the subject matter that Bennett had put into the piece was so prescient for now: between riot and famine, and fair shares and government corruption, you name it, it's all in it." He chuckles. "There are a lot of subversive elements in this show."
For Sir Cameron, sitting opposite me and giving a reluctant press interview just days before it started previewing last night, it is a case of déjà vu all over again. The theatre magnate holds the world record when it comes to producing new musicals, one of a number of global bests, including producing the three longest-running musicals of all time: Cats, The Phantom of the Opera and Les Misérables. At 64, he has been in the business for 45 years, amassing a fortune of some £600m en route, so I am curious about what prompted him to put his reputation on the line once more, especially his claim, more than a decade ago, that he was bowing out from the West End's front line.
In short, he couldn't help himself. Especially not when two old friends, George Stiles and Anthony Drewe, were the pair that Cowen and Lipman turned to for the lyrics and music.
"I read it, which I really wasn't doing to produce it; I was just going to tell them what I thought of it. And I went, 'My God! This is original.' And it took me about 20 seconds to make my mind up: would I be happy not to have done this show? No, I wouldn't, because it's so rare that you get this level of material." Two years and £2.5m later (a pittance compared with the jaw-dropping £40m-plus being spent on Spider-Man), Betty Blue Eyes is ready to go. "We're not going to open with a big advance, but," deep chuckle, "you know, none of my shows that are really original ever have! This has got the same kind of advance – very small – that I had with Les Mis and Cats. But they took off once word of mouth started."
And if it flops, at least Sir Cameron knows he'll be in good company. "Stephen Sondheim reminded me on Sunday [at last week's Olivier Awards] that just up the road, when Sweeney Todd opened, it didn't work; the press didn't like it." More laughter. "The public didn't come and it closed after a few months. Yet two or three years later, it started to have small productions, and it's been an acclaimed masterpiece ever since."
If all this laughter makes Sir Cameron sound like a genial sort of chap, well, he is, provided you don't cross him. Or make him cross, which is pretty much the same thing. With me, his flashpoint comes when I quiz him about the frankly extortionate cost of a night out in the West End. Top seats for some shows cost £85; an investment many theatre fans just can't afford – at least, not on a regular basis. Which is a shame given that Sir Cameron, along with his one-time musical partner Andrew Lloyd Webber, rightly claimed to have "completely reinvented, on a global scale, the appetite for musical theatre" back in the 1980s. He adds: "What we never, ever dreamt might happen, and has happened, is that going to the theatre is actually a cool thing to do now. The younger generation are not only happy to go and see shows; they want to be in them."
He insists it's "absolutely bollocks to think that you can't go to the West End for between 20 and 30 quid," adding: "That's the average price." Minutes later, he has me chasing after him on an impromptu tour of the Novello, one of seven theatres he owns in London, as he attempts to prove that the view even from the gods is as good as that from the stalls. My verdict? It is, but you can't stop the stage from getting smaller, and refurbished or not, just three cubicles in the Ladies' loos – the door to which he flings open with a flourish – still means a long and cramped queue come interval time.
He gets riled twice more: once when I attempt to peer through the mist that swirls over the goings on at his 14,000-acre estate in the Scottish Highlands, and again at the IoS photographer's attempts to snap him on the Novello's stage, with the Union Jack as a backdrop. ("I'm not doing it; I'm not interested in this sort of publicity," he huffs before relenting to pose in the theatre's foyer.)
Despite two arson attacks – the first, nearly 11 years ago, burned down his Scottish house, the second, earlier this month, turned a boat on his estate into a charred shell – Sir Cameron says it's "complete bollocks" to suggest that there's a problem. "What's been interesting is that the local council and the village are absolutely furious that there is a vandal out there doing things."
He is adamant that a protracted legal fight with one of the local crofters who wanted to buy some land that the producer had earmarked to develop has not soured relations locally. "It's ancient woodland. I've been restoring the ancient croft houses and we use them as holiday homes for people who want to go up there. It's been hugely successful to regenerate this area which would have otherwise died," he asserts.
Although he is a regular visitor to Scotland, I'm left with the sense that his heart lies in his 600-acre Somerset farm, which he shares with his partner, the Australian-born theatre photographer Michael Le Poer Trench. Certainly when I ask if casting his first movie, of Les Misérables, which is due to start shortly, will fulfil a dream, he retorts: "Dream? No. My dream is to be on my boat. Or on an island. Or in my house in the country. That's my dream." He insists he's never had any ambitions, beyond that of a wide-eyed eight-year-old captivated by a performance of Salad Days to go into the industry, "to thoroughly enjoy what I do."
Given that millions upon millions of people worldwide also thoroughly enjoy what he does, he is safe in adding: "Audiences aren't going to get rid of me. One thing I can say, with absolute certainty, is that my shows will still be performed when I'm dead, buried and forgotten. They're going to absolutely outlive me, which is a wonderful thing to think about." He will get an inkling next month if Betty Blue Eyes might be one of them.
1948 Cameron Anthony Mackintosh born in Enfield, north London, the eldest of three brothers. His father was a timber merchant and jazz trumpeter. His half-French, half-Maltese mother was a secretary.
1957 Sees the musical Salad Days and decides to be a musical producer.
1969 Stages first musical, Anything Goes. It flops.
1981 First teams up with Andrew Lloyd Webber to create Cats, which opens at the New London Theatre.
1985 Les Misérables opens at the Barbican Theatre in the West End, with The Phantom of the Opera opening the following year at Her Majesty's Theatre.
1990 Inaugurated the Cameron Mackintosh Chair of Contemporary Theatre at Oxford University.
1991 Wins an Olivier Award for his creative contribution to West End theatre and donations to productions.
1996 Is knighted for services to British theatre in the New Year's Honours list.
1999 Becomes the first producer to have four productions reach their tenth anniversary after Miss Saigon achieves the feat.
2006 Is honoured for his "outstanding contribution to tourism" in the UK.
2010 Celebrates the 25th anniversary of Les Misérables by staging a special performance at London's O2 arena and a new version of the show at the Barbican Centre.
2011 His first new musical in more than a decade, Betty Blue Eyes, opens. Plans celebration of Phantom's 25th anniversary in October.